R-22 and R-410A Operating Pressures on Air Conditioners! Checking the Charge!

in this hvac training video we're going over checking the charge and what pressures an r22 air conditioning system and an r410a air conditioning system operate at [Music] so we're going to be going over the pressure on the low side gauge and also on the high side gauge we're going to be going over those ranges now those ranges are patterns you got to remember that because it's going to be based on the indoor heat load for the low side gauge and for the high side gauge which is the red gauge that's going to be dependent on the outdoor heat load so it may be 70 degrees it may be 120 degrees outside so there's a lot more to this than just getting pressures on the low side gauge in the high side gauge but i am going to give you the ranges of the normal operation so that you know it should be within here to here for a system that is accurately charged so the first thing to know is that you have to let the system run for say at least 10 minutes before checking the charge it's really going to depend on the metering device as well if you have a txv or a piston but for the blue gauge which is connected to the large vapor line you're typically going to see for r22 a pressure of 58 psi to 85 psi if you're below 58 psi and you're like 55 or less that indoor coil is going to freeze there is a problem it could be a multitude of problems it may not just be a low refrigerant charge and you need to check some of our other videos in reference to that for the high side gauge it could be between 120 psi and 300 psi and it really depends on the outdoor temperature the outdoor heat load and that is a wide range right that's not very helpful now for r410a the low side gauge it should be between 102 psi to 145 psi once again if you're below 100 psi that indoor coil is freezing and i'm going to tell you why if you take a look at a pt chart so we have to be able to implement a pressure temperature chart anytime that we're checking the charge of an air conditioning system 102 psi equals a saturated temperature of about 32.5 degrees so say you're at 97 psi that equals 30 degrees what that's telling us is that the saturated refrigerant traveling through that indoor coil is below the temperature it takes for water to freeze and you got to remember there's water in the air crossing that quill so as the humidity in the air crosses the coil it'll freeze onto that quill and turn it into a solid block of ice so we really have a range of operation on that loci gauge of like 43 psi but it's more important than just kind of getting it in the middle so it's not a matter of like hey it's 80 degrees outside and i should set the indoor pressure at this and the outdoor pressure at this it's not that way no matter how much somebody wants it to be in fact for r410a you could be ranging on a pressure of 200 psi to all the way up to 480 psi you can't guess that range and the reality is if you do the system is going to run either inefficiently or it could be overcharged and you could have saturated refrigerant entering that compressor what that means is you don't have fully vapor refrigerant entering into the vapor compressor and it'll just kill the compressor so in order to get these pressures right we need to convert them to temperatures and so when we're converting these to temperatures there's also another layer that we need to take into consideration and that is what metering devices this unit have so before you even turn the system on and check the refrigerant charge with the gauges you need to see what metering device is in that indoor coil so if it's a piston then we're really going to be relying on the pressure on the blue loci gauge and the temperature on that large vapor line and if we have a thermostatic expansion valve then we're really going to be relying on the red gauge and the temperature on that small liquid line so we use the sub cooling method to check the charge of a system with a txv and we use the total superheat method anytime we have a piston with the blue gauge and the temperature on the large vapor line so what i really want you to get out of this is the pressures need to get converted to temperatures and once we do that it doesn't really matter what refrigerant we're dealing with anymore whether it's r22 or r4 tonight we take that pressure and we convert it to a saturated temperature so let's go ahead and do an example with r410i with a txv metering device what you need to know about a txv metering device is it's going to handle the temperature and pressure on loci gauge so we really need to check on the high side gauge so if we have a pressure on the high side gauge of 318.5 psi we need to convert that to a saturated temperature for r410a and we can do that either with a gauge face a calculation tool on your phone or on the pt chart like we show here and that converts to a saturated temperature of a degrees so if we read 90 degrees on that small liquid line you take 100 degrees as a saturated temperature in the middle of that outdoor coil minus 90 degrees on the tube exiting the coil and you're left with what's called 10 degrees of sub cooling now you compare the actual sub coin to what's on the reading plate for the outdoor unit and in this case we have a txv sub coin of 10 degrees so these outdoor units may have a range may have maybe three target sub coins or maybe just one target sub cooling and you're going to need to file that that's the average target sub coin for the unit now in this case we have 10 degrees of sub coin the system is calling for 10 degrees of sub coin so we are accurately charged so if we were anywhere from say 7 to 13 degrees of actual sub coin that is within three degrees of the target sub coin and that means that we're accurately charged i'm going to be going over two other scenarios the undercharge and overcharge scenario but you have to realize that a thermostatic expansion valve is going to control the pressure and temperature on the blue low side gauge so it's not going to matter if you add refrigerant into the system that blue gauge isn't even going to rise so you can't check the charge and think that hey i need to raise my pressure on the low side gauge so i'm going to add refrigerant it's not going to happen with a thermostatic expansion valve all you're going to do is you're going to increase the sub cooling on the high side so you could accidentally overcharge a system now i want to go over these other two examples if you had 96 degrees on the small liquid line and you still had 318.5 psi the 318.5 converted to a saturated temperature is 100 degrees minus the 96 degree line temperature and we're left with four degrees of sub cooling well that system would be undercharged because we don't have enough subcoin it needs more refrigerant in the system in another case say we have 318.5 psi converted to a saturated temperature of 100 degrees and we have a line temperature of 82. so we take 100 degrees minus 82 degrees and we're left with 18 degrees of sub cooling and that means that that system is overcharged so we'd have to have refrigerant removed out of the liquid line while the system's running if we needed to add refrigerant because the system is undercharged we have to put it into the low side of the running system so there's a lot of things involved with checking the charge and you even want to check the airflow before you even get started so i want you to be aware of all these scenarios so make sure you check out some of the free articles we have over at our website at ac services.com we go over the sub cooling method the total superheat method we go over operating pressures we go over a lot of those issues and we also have a refrigerant charging and service procedures for air conditioning book so that's available on our website and also on amazon and we have the full outline at ac servicestick.com ac book we go over all the old rules of thumb and why you shouldn't use them and we go over the preparation of a system for refrigerant checking the charge and also all the troubleshooting scenarios that you could run into in the field so that's it i hope you enjoyed the video and hope you enjoyed yourself we'll see you next time at ac service tech channel

Channel: AC Service Tech LLC

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Keywords: acservicetech, repair, maintenance, how to, fix, hvac, hvacr, how do you, test, ac, service, tech, check, measure, read, superheat, subcooling, refrigerant, procedure, voltage, temp, multimeter, freon, hvac class, hvac school, hvac training, r-22 pressure, r22 pressures, r410a pressures, 410a pressure, air conditioner pressure, r410a, r22, r-22, r-410A, air conditioning, freon leak, refrigerant leak, measuring freon pressure, manifold gauge set, pressure and temperature, superheat subcooling

Id: 5pQUkG43gAI

Length: 7min 41sec (461 seconds)

Published: Sat May 07 2022